How to Use the Command 'pw-cat' (with Examples)

The pw-cat command is a versatile tool for audio management that leverages PipeWire, an advanced multimedia server. pw-cat allows users to play and record audio files, offering various options to customize the playback and recording experience. This command is particularly useful for those who work with audio files, providing options to control quality, volume, and sample rate to suit diverse audio requirements. The following examples illustrate its use in a variety of contexts.

Use Case 1: Playing a WAV File Over the Default Target

Code:

pw-cat --playback path/to/file.wav

Motivation:

Imagine you have a WAV file that you want to play through your computer’s default audio output, be it headphones or speakers. This command allows you to effortlessly play the audio file without needing to open additional applications, making it simple and efficient, especially when handling multiple audio files or scripting batch operations.

Explanation:

• --playback: This flag tells pw-cat to play the specified audio file through the default audio sink on the system.
• path/to/file.wav: This is the path to the WAV file you wish to play. Replace path/to/file.wav with the actual file path of your audio file.

Example Output:

When this command is executed, it will play the specified WAV file through the default audio device. You will hear the audio output through your speakers or headphones. No textual output will be shown on the terminal.

Use Case 2: Playing a WAV File with a Specified Resampler Quality

Code:

pw-cat --quality 0..15 --playback path/to/file.wav

Motivation:

This example is ideal for audiophiles or professionals requiring high audio fidelity. By defining the resampler quality, you control how closely the output audio resembles the original audio file when PipeWire processes it, such as when converting sampling rates.

Explanation:

• --quality 0..15: This argument specifies the resampling quality level, where 0 is the lowest and 15 is the highest. Higher values usually offer better audio quality at the cost of more CPU usage.
• --playback: As in the first use case, this tells pw-cat to play the audio file.
• path/to/file.wav: Similar to the previous example, this is the path to the WAV file to be played.

Example Output:

Executing this command will play the audio file with the specified resampling quality. Again, you hear the output through your audio device without textual feedback in the terminal.

Use Case 3: Recording a Sample with Volume Level of 125%

Code:

pw-cat --record --volume 1.25 path/to/file.wav

Motivation:

Suppose you need to record an audio file with a higher gain to ensure audibility or when the source is naturally quiet. This command allows boosting the volume by 25% during the recording process, which is helpful when preparing audio content for environments with variable sound requirements.

Explanation:

• --record: Indicates that the tool should be used to record audio instead of playing it back.
• --volume 1.25: Adjusts the recording gain to 125% of the original input, effectively amplifying the sound.
• path/to/file.wav: This is the file path where the recorded audio will be saved.

Example Output:

When this command is used, it records audio from the default input device at 125% volume, saving it to the specified path. You would not see any textual output during the process.

Use Case 4: Recording a Sample Using a Different Sample Rate

Code:

pw-cat --record --rate 6000 path/to/file.wav

Motivation:

There might be instances where a specific sample rate is required for compatibility with other systems or for experimenting with audio processing. This use case illustrates how to choose a non-standard sample rate during recording to meet such demands.

Explanation:

• --record: Directs the tool to initiate the recording process.
• --rate 6000: Sets the sample rate for recording to 6000 Hz, which is different from the standard (often 44100 or 48000 Hz). This atypical rate might be for special audio processing needs.
• path/to/file.wav: Specifies where to store the recorded file.

Example Output:

The system will record audio using the specified sample rate and save it at the provided location. As with previous examples, the terminal does not display any textual information during recording.

Conclusion:

The pw-cat command offers a flexible approach to handling audio files within PipeWire, enabling playback and recording with various options tailored to different use cases. By manipulating parameters such as resampling quality, volume, and sample rate, users can cater to specific audio requirements efficiently. With these examples, users can understand and exploit pw-cat’s potential for audio file manipulation on systems using PipeWire.